EFFECTS OF DIETARY IRON CONCENTRATION ON THE PERFORMANCE AND MEAT COLOR OF GRAIN-FED CALVES

Abstract

Forty-two black and white male dairy calves were used to determine the effect of iron concentration in concentrate diets on growth performance and meat color. The experimental period began after weaning at 6 wk of age. Calves, averaging 67.2 kg, were randomly divided into three groups. Each group received, ad libitum, concentrates with different iron concentrations: low iron concentration, 100 mg kg−1 of dry matter (LI, n = 15), intermediate iron concentration, 150 mg kg−1 (II, n = 14) and a high iron concentration, 200 mg kg−1 (HI, n = 13). Calves were slaughtered at 190 kg body weight. Total iron intake averaged 30.0, 56.1 and 74.7 g for groups LI, II, HI, respectively. Iron concentration in the diet did not affect (P > 0.10) average daily gain or total dry matter intake, which averaged 1.23 kg d−1 and 334.5 kg, respectively. Blood samples were collected from the jugular vein on days 1, 29, 57 and on the day of slaughter. Hemoglobin concentration and hematocrit averaged, respectively, 11.9 g 100 mL−1 and 37% on slaughter day and were not affected (P > 0.10) by treatments. Carcass weight and classification, color of the pectoralis major, and composition of the liver and of the longissimus dorsi at the 12th rib level were not affected (P > 0.10) by treatments. Unexpectedly, color score of the longissimus dorsi was linearly (P < 0.05) related to iron concentration of the diet, likely due to random error as calves fed the HI diet had the lighter meat color. In conclusion, concentrates containing 100–200 mg g−1 of iron, exceed the iron concentration required to produce light meat color or affect hemoglobin concentration of grain-fed calves. Therefore, concentrates made using commercial ingredients would need the addition of an agent-chelating iron to produce light meat color. Key words: Iron, calves, growth, meat, liver, color, hemoglobin